Types of Congenital Heart Defects
The profile of Congenital Heart Defects vary depending upon the age group, ranging from simple defects to
complex ones which generally arise due to combination of many simple complications;
improper location of the blood vessels which move to and from the heart, erroneous
developmental process of heart, etc. These defects range from simple "holes" between
heart chambers to severe malformations like complete absence of one or more of the
heart's chambers or valves and hence can be broadly classified as:
I. Acyanotic Congenital Heart Defects or Left-to-right shunts
These include deviations from the normal cardiac shunt wherein there is a balance between
the systemie and pulmonary circulations. The left-to-right shunts cause back-leak of blood
from the systemic to the pulmonary circulation leading to an increase in blood pressure as
well as volume in the latter. These septal defects being very common in newborns, don't
normally interfere with the amount of oxygen or Blood that reaches the body tissues. These
Congenital Heart Defects are asymptomatic or show mild to severe symptoms which can either have an acute or
delayed onset, and can be further sub-divided into:
Ventricular septal defect (VSD)
VSD results due to presence of a defect or hole in the membranous part of the
interventricular septum which forces blood from the left side of the heart to the
right side at every heartbeat. Oxygen-rich blood reverts to the lungs, thereby
hampering the entry of the not yet oxygen-rich blood to the lungs. Since huge
volume of blood enters the lungs, the heart pumps extra blood making VSD
affected newborns easily fatigued.
Atrial septal defect (ASD)
One of the least complex forms of Congenital Heart Defects, ASD is characterised by a hole or defect
between the atria leading to leakage of oxygen-rich blood to the right side of the
heart which pushes it back to the lungs increasing the blood flow significantly.
ASDs primarily include secundum defect (hole in the middle of atrial septum),
primum defect (associated with a cleft in the mitral valve causing blood leakage)
and sinus venosus defect (leads to abnormal drainage from the right upper pulmonary vein).
Atrioventricular canal defect (AVCD)
One of the most complex Congenital Heart Defects, AVCD can be best elucidated as a large hole in the middle of
the baby's heart. Lack of differentiation of atria and ventricles into separate chambers, and of
the mitral and tricuspid valves into two separate valves leads to formation of a large connection
between the two atria, two ventricles and an AV valve where separate mitral and tricuspid valves
should exist. AVCDs become more complicated when there is an
improper formation of one of the ventricles, an obstruction to aorta or straddling valves;
which increases the blood flow to lungs through septal defects damaging the heart's blood
vessels. Regurgitation of valve occurs upon blood leakage from ventricular chambers to atrial
chambers due to its improper closure, leading to heart enlargement.
Patent ductus arteriosus (PDA)
PDA occurs when there is failure of normal physiologic closure of ductus arteriosus post baby's
birth and there is a persistent connection between the aorta and pulmonary artery, leading to
excessive blood flow to the lungs damaging heart's blood vessels. PDA can be asymptomatic or
in severe cases, may result in congestive heart failure with increasing age.
II. Right/Left heart obstructive defects
Obstructive defects result due to abnormal blockage or narrowing of heart valves, arteries or
veins, thereby leading to heart enlargement and hypertension; its common sub-types are:
Pulmonic stenosis
Occurs with a combination of other Congenital Heart Defects and is a fixed or dynamic anatomic impediment
of blood flow from heart's right ventricle to the pulmonary artery causing mild to moderately
severe desaturation or cyanosis.
Aortic stenosis
There is narrowing of the aortic valve (aorta is the main artery that carries blood out of the
heart to the rest of the body) opening that leads to aortic stenosis, making the left ventricle
to pump blood harder. Thus, the blood doesn't flow freely to the aorta causing high blood
pressure subsequently decreasing blood flow from the heart.
Coarctation of the aorta
A very common CHD, and is characterised by narrowing of a discrete or long segment of aorta and
if undiagnosed leads to congestive heart failure in infants. This condition causes significant
afterload on the left ventricle resulting in increased wall pressure and ventricular hypertrophy.
III. Cyanotic Congenital Heart Defects/Right-to-left shunt
In these, deoxygenated blood bypass the pulmonary circulation (lungs) and enters the systemie
circulation, causing mixing of oxygenated and deoxygenated blood leading to right-to-left shunting
and pulmonary venous desaturation. This collateral circulation increases pulmonary vascular
resistance resulting in cyanosis.
Tetralogy of Fallot (TOF)
TOF is a combination of four heart defects namely, VSD, pulmonic stenosis, right ventricular
hypertrophy and overriding of aorta, which together obstruct pulmonary blood flow leading
to pumping of a mixture of oxygenated and deoxygenated blood throughout the body. A child
with unrepaired TOF may often feel dizzy and fatigued along with an
impending risk of arrhythmia and endocarditis.
Transposition of the great arteries (TGA)
A serious yet rare condition arising due to reversal of the two main arteries which exit the
heart; in short they are transposed. This leads to parallel circulation and complete admixture
of the pulmonary and systemic venous returns, eventually pumping low-oxygenated blood to
the body through aorta. Infants don't survive unless there are inter circulatory shunts through
septal defects.
Tricuspid atresia
This condition is characterised by an absence of the tricuspid valve (between the right atrium
and ventricle) causing left ventricular hypertrophy due to absence of proper connection between
the right atrium and right ventricle. Progressive cyanosis occurs in the newborn since the first
day of life. In such cases, presence of other anatomical variations like ASD or VSD contributes to
symptom development as well as treatment efficacy.
Eisenmenger complex
This condition highlights a stage in the CHD, when pulmonary Hypertension becomes irreversible
and the defect becomes inoperable. An initial high blood pressure on left ventricle creates left-to-
right shunt, causing pulmonary hypertension by increasing the blood flow to lungs through
pulmonary artery. Injured lung arterioles increase blood flow resistance gradually until the shunting
direction is reversed to right-to-left through VSD, causing cyanosis.
Causes of Congenital Heart Defects
Multiple factors are responsible for altering the developmental process of heart during the
initial stages of fetus development but in most the specific cause of a CHD is unknown.
Genetic factors:
50% of newborns with trisomy 21 and nearly all trisomy 18 affected, acquire atrial or
ventricular septal defects or AV canal lesions whereas the risk of Congenital Heart Defects increases to 80%
in trisomy 13 affected newborns. One third of females with Turner syndrome exhibit left/
right heart obstructive defects whereas 50% of 47 XXY males (Klinefelter syndome) show
PDA and other septal defects. Single gene mutations in GATA4, NKX2.5, Myosin heavy chain
6 gene (MYH6), etc. and copy number variations have been linked to isolated Congenital Heart Defects like atrial
septal defects.
Lifestyle factors:
Uncontrolled and poor management of maternal infectious diseases like rubella or Syphilis,
conditions like Diabetes, maternal iodine and folic acid deficiencies; alcohol and drugs intake
increase the risk of Congenital Heart Defects.
Environmental exposures:
During the 1" trimester, exposure to anticonvulsant or dermatological medications, industrial
chemicals, radiation or lithium salts for manic-depressive illness may cause structural
abnormalities in fetus's heart.
Signs and Symptoms of Congenital Heart Defects
During pregnancy exchange of oxygen and carbon dioxide takes place via the placenta and
not through the fetus's lungs, thus preventing development of any breathing complications
due to severe underlying heart defects until circulation transitions in the newborn state post-
birth. Early signs and symptoms of Congenital Heart Defects depend on severity of its type which often go
undetected until later in life while other Congenital Heart Defects initially manifest by the presence of:
- Heart murmur
- Lung congestion
- Shortness of breath and dehydration
- Rapid breathing in case of TOF and TGA
- Fatigue and fussiness
- Cyanosis
- Respiratory tract infections
- Under development of limbs and muscles
- Poor weight gain, feeding, growth and development
- Cardiac failure in severe Congenital Heart Defects
Diagnosis of Congenital Heart Defects
Congenital Heart Defects are often suspected in newborns post-birth or in a few weeks, if cyanosis or
heart murmurs are present. A pediatric cardiologist conducts physical examination
for confirming symptoms upon listening to the child's heart and lungs with a stethoscope.
Imaging Tests for Congenital Heart Defects
Fetal Echocardiography
This test is recommended to confirm cases of suspected CHD. This echo test acquires a
complete motion picture of the baby's heart using sound waves between 18-22 weeks of
pregnancy, to identify abnormalities in the heart muscle and valves.
Electrocardiogram (ECG or EKG)
ECG test can diagnose enlargement of heart chambers by recording the heart's electrical
activity, its beating and rhythm (steady or irregular)
Chest X-Ray
This provides accurate pictures of heart and lungs aiding in diagnosing extra fluid
accumulation or extra blood flow in lungs along with probing for heart chamber
enlargement.
Pulse Oximetry
A small sensor attached to the finger or toe can provide an estimate of oxygen concentration in
blood, where too little levels aid in detecting severe heart problems.
Cardiac Catheterisation
A flexible thin tube - catheter is inserted into the baby's vein in arm, groin or neck, then
threaded to the heart followed with an injection of a special dye through the catheter, into
the blood vessel or heart chambers which enables the cardiologist to measure the pressure
and oxygen levels inside to identify cases of blood mixing.
Treatment and Management of Congenital Heart Defects
Sometimes, mild Congenital Heart Defects like small holes may correct themselves with increasing age, but the
severe ones need immediate treatment upon diagnosis. Depending on the type, a cardiac
surgeon uses catheterisation to repair septal defects or narrowed valves without surgically
opening the chest and heart. If catheterisation fails, open heart surgeries are performed which
involve opening the chest and stopping the heart temporarily for repair. If a serious defect is
irreparable, heart transplants are performed. If Congenital Heart Defects are diagnosed in childhood or adulthood,
along with the combination of other treatments, certain medications like angiotensin-converting
enzyme inhibitors, beta blockers, diuretics, etc. are also prescribed to ease stress on heart by
lowering blood pressure and fluid accumulation in chest.
An early diagnosis though mitigates future complications and increases life expectancy of the
affected, a speedy recovery only entails upon effective manage ment of the patient. Severe CHD
affected kids require multiple corrective surgeries throughout life with ongoing care and support
from families along with scheduled follow-up with their cardiologist. Certain restrictions must be
exercised like limiting strenuous physical activities. In case of prosthetic devices implantation like
heart valves, antibiotics must be taken to prevent infections. Congenital Heart Defects can't be prevented but following
few precautionary measures can reduce their risk, if exercised by women before/during Pregnancy.
Get vaccinated against Rubella infection before you try to conceive.
Intake of multivitamin tablets with folic acid is a must to reduce birth defects.
Abstain from alcohol or drugs and other chemical
exposure activities like painting, etc.
Control and manage chronic conditions like diabetes, epilepsy, etc
After facing two surgeries and pulmonary valve replacement, Asha now a software engineer and
a mother of a healthy daughter, belongs to one of the first few TOF survivors. Individuals with
CHD need lifetime monitoring since their healthcare needs are still under research with an
unknown prognosis and life expectancy.
Contrary to their sizes, it's frightening to even imagine a
little innocent one suffering from something grave. It is time the big hearts in us reach out to
help them cope with something, which scarred their life even before their birth .
